The present invention relates to a process for the production of molded parts and fillings made of rigid and flexible polyurethane foams and rigid polyurethane foams with isocyanurate structures.
In processes for the manufacture of molded parts, filling mold cavities, and discontinuous panel production from foam-forming mixtures, the output rate of the foam machines is generally kept high enough that the required amount of reaction mixture is charged in the shortest possible time. This is done to achieve the narrowest possible age spectrum of the reaction mixture so that the curing process will start simultaneously throughout the mold.
If relatively large parts are to be produced in molds or large cavities are to be filled with foam or panels are to be produced discontinuously, fairly long pouring times are necessary unless the filling is carried out in several shots. In either case, the age spectrum of the finished foam broadens. Variations in the gross density of the finished foam and anisotropy of the cell structure occur due to the running-under or rolling-over of the foaming reaction mixture. There is also a lack of dimensional stability in the disturbed zones of the foam.
The problem of eliminating or compensating for losses of quality due to an extended age spectrum of the reaction mixture is addressed by the present invention.